[poly-gets-updated-coords] docs(changeset): Bugfix to ensure that the Interactive Graph Editor updates the Polygon start coords if the number of sides change. (#2283)

## Summary:
This PR is part of the Interactive Graph project. 

The purpose of this simple PR is to implement a fix that ensures that the start coords are always updated when content creators update the number of sides for the graph. 

Issue: LEMS-2883

## Test plan:
- manual testing

Author: SonicScrewdriver

Reviewers: nishasy

Required Reviewers:

Approved By: nishasy

Checks: ✅ 8 checks were successful, ⏹️  5 checks were cancelled

Pull Request URL: #2283

Author: SonicScrewdriver

.changeset/cuddly-snails-work.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/perseus": patch
+---
+
+Bugfix to ensure that the Interactive Graph Editor updates the Polygon start coords if the number of sides change.

packages/perseus-editor/src/widgets/interactive-graph-editor/interactive-graph-editor.tsx

@@ -510,6 +510,7 @@ class InteractiveGraphEditor extends React.Component<Props> {
                                                 numSides:
                                                     parsePointCount(newValue),
                                                 coords: null,
+                                                startCoords: undefined,
                                                 // reset the snap for UNLIMITED, which
                                                 // only supports "grid"
                                                 // From: D6578